> It's a well-established, economically rational business model to subsidize prices in order to gain market share.

Because once they have the market share, they raise prices and/or make the product worse in order to get their money back.

> And users don't really need to be concerned. Just enjoy the low prices. If the service you use goes out of business, it's pretty easy to switch to another.

Well that's the question, isn't it? If the market stays healthy and they don't take the oxygen out of the room and kill the competition and switching costs stay low, then yes by all means enjoy the free ride but plan for its end. But... do plan for it.